Engineeringphysical tokamak T15 MD and steady state injection

Engineering-physical tokamak T-15 MD and steady state injection Azizov E. A. , Leonov V. M. , Panasenkov A. A. , Tilinin G. N. , Khvostenko P. P. RRC “Kurchatov institute”, Institute of physics of tokamaks OS 2010, 5 - 9 July, Novosibirsk 1

As a result of teamwork of researchers from different countries the direction of movement to a power thermonuclear reactor construction is now chosen. The Russian Federation, being the active participant of international project ITER, is interested in expansion of base for experimental works on controlled thermonuclear fusion (CTF). The accelerated development of world nuclear power engineering intensifies problems of its raw maintenance and recycling of wastes. Attraction to the decision of these problems of the controlled thermonuclear fusion is one of the opportunities actively discussed today. OS 2010, 5 - 9 July, Novosibirsk 2

Introduction of CTF in nuclear power is possible by its inclusions in a cycle of nuclear fuel production (“breeding”) for traditional nuclear power, and also by "reburning" its wastes - minor actinides. Both directions become technically possible, if into a contour of fast (14 Me. V) neutrons utilization (“blanket”) of the CTF reactor to enter fissible materials, that is to use the CTF reactor as a thermonuclear source of neutrons (TSN or a “hybrid reactor”). In that way the important step to practical application of CTF can be done. OS 2010, 5 - 9 July, Novosibirsk 3

For expansion of research subjects in support of nuclear and thermonuclear power, it is necessary to have in Russia compact tokamak with: • flexible ITER-like configuration of magnetic field, • extended (k ≤ 2) divertor plasma, • ability to control the shape and parameters of a plasma in a real time. Installation should be equipped by a complex of additional plasma heating and current drive (Paux 10 -15 МВт), providing simultaneous achievement of high plasma temperature (Ti ~ Te ~ 5 -9 кэ. В) and density (ne ~ 1020 m-3), and also allowing to control plasma profiles at completely non-inductive current drive. Reliable realization of such operating modes is the primary goal of the offered project - Engineering-Physical Tokamak (EPT - T-15 MD). OS 2010, 5 - 9 July, Novosibirsk 4

Based on a level of possible financing and available resources, Т -15 MD will be the installation of a modern level constructed within the nearest 5 -6 years. Such project can become the center of researches in Russia under program of CTF on the basis of tokamaks. Program Т-15 MD includes studying of possible ways for economic efficiency increase of thermonuclear reactors, including its work in the two-component mode necessary for TSN. The wide program of works in modes with the improved parameters of plasma (raised times of energy and particles confinement and high βN) and demonstration of a stationary mode (t> tskin) of the plasma discharge is considered. OS 2010, 5 - 9 July, Novosibirsk 5

T-15 MD configuration - section view OS 2010, 5 - 9 July, Novosibirsk 6

Aspect ratio 2. 2 Plasma current IP, МА ≤ 2. 0 Major radius of plasma column R, m 1. 40 Minor radius of plasma column а, s 0. 64 Elongation of plasma column k 95 1. 8 Triangularity of plasma column δ 95 0. 3 -0. 5 Pulse duration t , s 5 Toroidal field on axis Bt, T 2. 0 Safety factor of plasma column q 95 3 -5 Number of toroidal coils 16 Poloidal flux CS , Wb ~5 Limit of plasma density 1020 m-3 1. 6 Nominal plasma density 1020 m-3 0. 5 Peak electron temperature ke. V ~9 Peak ion temperature ke. V ~9 Neutral beam power MW 8 Energy of beams ke. V Power of ECR heating (f=110 GHz), MW OS 2010, 5 - 9 July, Novosibirsk 75 -80 Discharge start and plasma current rise is to be produced by inductive way. At about nominal value of the current transition to non-inductive current drive should be provided. Quasi-stationary regime for Т-15 MD corresponds to pulse duration of 5 -10 s at a level of the plasma current ~1 МА. This requires application of powerful systems of the plasma heating and current drive, and also divertor for removal of power introduced into the plasma. Tangential injection of fast hydrogen atoms with energy 75 -80 ke. V and ECR heating at frequency 110 GHz are chosen. 6 7

Preliminary calculations of achievable plasma parameters in a case of the NB injection and also for combined heating NB + ECR were done Pictures demonstrate dependence of 1) injected beam power absorbed by the plasma and generated non-inductive current fraction on the average plasma density and 2) profiles of the absorbed power over relative plasma column radius for different average plasma densities (in units of 1019 m-3 ) for injection of 8 MW hydrogen atoms with energy 80 ke. V in hydrogen plasma at toroidal field 2 Т and the plasma current 2 МА: - injected power is completely absorbed by the plasma at density above 5*1019 m-3; - generated non-inductive current fraction is at a level of 1 МА at density of 2*1019 m-3 ; - at moderate plasma density injected NB power is absorbed in internal areas. OS 2010, 5 - 9 July, Novosibirsk 8

Long-pulse mode of Т‑ 15 MD operation is possible despite of not too big capacity of magnetic flux in an inductor. One variant of such mode is presented in figure where the plasma total current is 1 МА, average density is 3*1019 m-3 and toroidal field is of 2 T. NB power is 8 MW and for increase of electron temperature and improvement of the plasma current generation by the beam, ECR power of 7 MW is additionally entered approximately in the middle of the plasma radius. In this mode the beam generated current fraction is INBI ~ 60 %, the bootstrap current is IBS ~ 22 %, the rest is an ohmic current. OS 2010, 5 - 9 July, Novosibirsk 9

Installation Т-15 MD will use three existing injectors from Т-15 tokamak and one more new. Series of ion sources IVIS with working parameters 60 k. V/60 A/1 s had been prepared for work in the T-15 neutral beam injection system. Ion Sources Ion Dump Valve 100/30 cm CAL Magnet Cryo Pump NB Injector of T-15 installation OS 2010, 5 - 9 July, Novosibirsk Ion source IVIS for T-15 injectors 10

All NBI components, namely neutraliser, residual ion deflecting magnet, ion dump, cryo-pumps and NB movable calorimeter, can work in steady-state regime when NB power of 3 MW is producing. The ion source requires modernization as it was designed for 1. 5 s beam-on pulses and can not operate with long pulses. The reasons are as follows: -Use of DC heating of tungsten filament cathodes leads in a case of long-pulse operation to their overheating. -The source arc chamber is made of stainless steel and its cooling is calculated for work with the pulse duration of no more than 5 s. -Electrodes of ion-optical system (IOS) which provides extraction and formation of ion beam with small divergence angle at a level of ± 1÷ 1. 5 о are multi-slot grids with peripheral cooling that limits pulse duration to 1. 5 -2 s. OS 2010, 5 - 9 July, Novosibirsk 11

Modernized ion source IVIS‑CS for application in the Т-15 MD injectors is under development, in which: - design of cathode block is changed for three-phase AC heating of filament groups. “Old” arc chamber with new cathode block has been tested with increased up to 5 s arc pulses; -new arc chamber is designed with configuration similar to Japanese “Kamaboko” with the case made of copper and cooling which provides steady state work at power up to 150 k. W; - design of multi-aperture (with shaped round apertures) three-electrode IOS with internal cooling channels is under development. The transparency of such electrodes is about 35 %. So, IVIS-CS source should provide extraction of hydrogen ion beam with a current of 40 A. OS 2010, 5 - 9 July, Novosibirsk Arc chamber of IVIS-CS. 12

Biological Shield NBL Tokamak 21 m 28 m Plan view of T-15 MD installation OS 2010, 5 - 9 July, Novosibirsk 13